C++ Primer Plus

Like C, C++ began its life at Bell Labs, where Bjarne Stroustrup developed the language in the early 1980s. In Stroustrup’s own words, “C++ was designed primarily so that my friends and I would not have to program in assembler, C, or various modern high-level languages. Its main purpose was to make writing good programs easier and more pleasant for the individual programmer” (Bjarne Stroustrup, The C++ Programming Language, Third Edition. Reading, MA: Addison-Wesley, 1997).

Bjarne Stroustrup’s Home Page

Bjarne Stroustrup designed and implemented the C++ programming language and is the author of the definitive reference manuals The C++ Programming Language and The Design and Evolution of C++. His personal website at AT&T Labs Research should be the first C++ bookmark, or favorite, you create:

www.research.att.com/~bs

This site includes an interesting historical perspective of the hows and whys of the C++ language, Stroustrup’s biographical material, and C++ FAQs. Surprisingly, Stroustrup’s most frequently asked question may be how to pronounce Bjarne Stroustrup. Check out the FAQ on Stroustrup’s website and download the .WAV file to hear for yourself!

Stroustrup was more concerned with making C++ useful than with enforcing particular programming philosophies or styles. Real programming needs are more important than theoretical purity in determining C++ language features. Stroustrup based C++ on C because of C’s brevity, its suitability to system programming, its widespread availability, and its close ties to the Unix operating system. C++’s OOP aspect was inspired by a computer simulation language called Simula67. Stroustrup added OOP features and generic programming support to C without significantly changing the C component. Thus C++ is a superset of C, meaning that any valid C program is a valid C++ program, too. There are some minor discrepancies but nothing crucial. C++ programs can use existing C software libraries. Libraries are collections of programming modules that you can call up from a program. They provide proven solutions to many common programming problems, thus saving you much time and effort. This has helped the spread of C++.

The name C++ comes from the C increment operator ++, which adds one to the value of a variable. Therefore, the name C++ correctly suggests an augmented version of C.

A computer program translates a real-life problem into a series of actions to be taken by a computer. The OOP aspect of C++ gives the language the ability to relate to concepts involved in the problem, and the C part of C++ gives the language the ability to get close to the hardware (see Figure 1.2). This combination of abilities has enabled the spread of C++. It may also involve a mental shift of gears as you turn from one aspect of a program to another. (Indeed, some OOP purists regard adding OOP features to C as being akin to adding wings to a pig, albeit a lean, efficient pig.) Also because C++ grafts OOP onto C, you can ignore C++’s object-oriented features. But you’ll miss a lot if that’s all you do.

Figure 1.2. C++ duality.

Only after C++ achieved some success did Stroustrup add templates, enabling generic programming. And only after the template feature had been used and enhanced did it become apparent that templates were perhaps as significant an addition as OOP—or even more significant, some would argue. The fact that C++ incorporates both OOP and generic programming, as well as the more traditional procedural approach, demonstrates that C++ emphasizes the utilitarian over the ideological approach, and that is one of the reasons for the language’s success.

Portability and Standards

Say you’ve written a handy C++ program for the elderly Pentium PC computer running Windows 2000 at work, but management decides to replace the machine with a new computer using a different operating system, say Mac OS X or Linux, perhaps one with a different processor design, such as a SPARC processor. Can you run your program on the new platform? Of course you’ll have to recompile the program using a C++ compiler designed for the new platform. But will you have to make any changes to the code you wrote? If you can recompile the program without making changes and it runs without a hitch, we say the program is portable.

There are a couple obstacles to portability, the first of which is hardware. A program that is hardware specific is not likely to be portable. One that takes direct control of an IBM PC video board, for example, speaks gibberish as far as, say, a Sun is concerned. (You can minimize portability problems by localizing the hardware-dependent parts in function modules; then you just have to rewrite those specific modules.) We avoid that sort of programming in this book.